McGee, a leader of the Youth Rangers, gives his den a tour of the NCIS headquarters; Abby, while demonstrating her lab equipment, takes a fingerprint from a talkative boy, Carson, and runs it through the AFIS program, which finds a positive match, saying that Carson had become abducted while a small child. Carson's ostensible mother is a Navy lieutenant on active duty. Gibbs and company investigate; they uncover the history of Carson, his biological parents, and a custodial grandmother; Abby learns that police want his father for murder. Two detectives from the Metro PD deliver evidence and join the case. Another murder takes place, then the gang nab the two-time killer.